PARIS -- Presidential candidates Marine Le Pen and Emmanuel Macron fought over fish and Europe's future as they courted France's blue-collar vote Thursday in an increasingly charged campaign.

A day after "the battle of Whirlpool," when Le Pen upstaged Macron at a home appliance factory threatened with closure, she was up before dawn to cruise aboard a fishing trawler on the Mediterranean. It was her latest TV-friendly effort to portray herself as the candidate of workers against Macron, a centrist former banker and economy minister she paints as the candidate of the financial, political and pro-EU elite.

"My grandfather was a fisherman, so I am in my element," Le Pen said after her voyage aboard the trawler Grace of God 2.

She said France will take back control of its maritime policies if she is elected in the second-round vote May 7. She again tore into Macron's more pro-market, free-trade economic program.

Macron fired back on Twitter, saying Le Pen's proposals to take France out of the European Union would sink France's fishing industry.

"Have a nice trip. Europe's exit she proposes, it's the end of French fishing. Think about it," he tweeted, before visiting the ethnically mixed Paris suburb of Sarcelles.

As he met with Sarcelles residents, Macron called Le Pen's National Front party "xenophobic."

"There's Marine Le Pen's project of a fractured, closed France. ... On the other hand, you have my project which is a republican, patriotic project aiming at ... reconciling France," he said.

Macron went to a gymnasium to meet members of an association that works to socially integrate local youths through sports and by helping them set up businesses and find jobs.

Later, speaking on TF1 television, Macron dismissed Le Pen's appearance at the Whirlpool plant as a "communication stunt in a parking lot." He insisted that nationalizing Whirlpool, as Le Pen suggested, "won't work."

He said he admires Le Pen's "determination" but called her National Front as a "party of hate."

Le Pen took her campaign later to the Mediterranean city of Nice, where 86 people were killed in an Islamic extremist truck attack last year, and pledged to "tame" globalization and protect workers.

Many voters can't stomach either candidate. French high school students scuffled with riot police in a cloud of tear gas during a Paris protest at which they painted Le Pen as an extreme nationalist with dangerous views and Macron as too cozy with the finance world.

Students blocked entrances to some high schools and marched through eastern Paris to the Bastille neighbourhood, the heart of the 1789 French revolution. Most of the protesters were peaceful, but a few clashed with riot police ringing the crowds.

Many of the students aren't old enough to vote, yet they reflect a chunk of the French electorate that is expected to sit out the May 7 election, either because of dislike for both candidates or on the assumption that Macron will win.

While Macron has been considered the favourite for the runoff, pollsters have long noted that a very low turnout could propel Le Pen into the presidency -- a risk Macron stressed Thursday.

"Let's all face our responsibilities," he said, arguing that not voting would help Le Pen and amount to casting a ballot to abandon the EU, the euro currency and "the nation and its values."

Le Pen's surprise visit to the threatened Whirlpool clothes-dryer factory in northern France on Wednesday put Macron on the defensive and prompted him to also meet with angry Whirlpool workers later the same day.

Macron was whistled and booed when he first arrived. But he stood his ground, patiently and at times passionately debating workers in often heated exchanges about how to stop French jobs from moving abroad.

Associated Press writers John Leicester and Thomas Adamson in Paris and Alex Turnbull in Nice contributed to this report.